TOKYO — Japanese leaders reacted angrily Friday after police on Okinawa said a U.S. Air Force serviceman was suspected of breaking into an apartment while drunk and punching a schoolboy, just weeks after two U.S. sailors were accused of raping a woman on the same island.

The trespassing and assault took place early Friday, police said. The airman was apparently in violation of a curfew imposed last month by the U.S. military on all of its roughly 50,000 military personnel in Japan after the rape accusation.

The police did not release the name of the 24-year-old airman, who was hospitalized after falling to the ground from a third-story window.

The back-to-back episodes have stirred outrage on Okinawa, the southern Japanese island that hosts three-quarters of the U.S. bases in Japan. The episodes also threaten to complicate ties between the United States and its closest Asian ally at a time both nations are trying to work together to face a growing challenge from China.

The episodes have added to Okinawa’s increasingly vocal opposition to what many islanders see as an oversized U.S. base. Japanese officials fear Okinawan anger could grow strong enough to disrupt their nation’s overall security alliance with the United States, on which Japan has relied for its defense since the end of World War II.

The governor of Okinawa, Hirokazu Nakaima, warned that the actions by U.S. servicemen threatened the entire U.S.-Japan alliance.

U.S. officials said they would cooperate with the investigation. “We are very upset, and we pledge complete cooperation with the government of Japan,” said the U.S. ambassador to Japan, John Roos.

Crimes by U.S. military personnel are an emotional issue on Okinawa, especially since the 1995 rape of a schoolgirl by three servicemen. They top a list of Okinawan complaints about the bases that also includes noise, risk of accidents and pollution.

The police said the U.S. airman was suspected of entering the apartment at about 1 a.m. Friday as two schoolboys inside were sleeping. The American woke them up and punched one of them, age 13, in the face, the police said, and then tried to flee through the window.

They said the American had apparently been drinking at a bar on the ground floor of the same building.